Polyoxadiazole composite fibers

ABSTRACT

The present invention is directed to preparation of a polyoxadiazole composite fiber and a flexible chain polymer which is not a polyoxadiazole polymer and articles produced therefrom.

BACKGROUND OF THE INVENTION

The present invention is directed to preparation of a polyoxadiazolecomposite fiber and articles produced therefrom.

A need is present for a composite fiber comprising polyoxadiazole whichexhibits dyeability and improved UV stability.

SUMMARY OF THE INVENTION

The present invention is directed to a composite fiber comprising apolyoxadiazole polymer and a flexible chain non-polyoxadiazole polymer.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to composite fibers of a polyoxadiazoleand a flexible chain polymer and the preparation thereof.

For purposes herein, the term “fiber” is used herein interchangeablywith “filament”, and means a relatively flexible, macroscopicallyhomogeneous body having a high ratio of length to width across itscross-sectional area perpendicular to its length. The fiber crosssection can be any shape, but is often somewhat circular. Fiber spunonto a bobbin in a package is referred to as continuous fiber. Fiber canbe cut into short lengths called staple fiber. Fiber can be cut intoeven smaller lengths called floc. Multifilament yarns can be combined toform cords. Yarn can be intertwined and/or twisted.

The term spin as used herein refers to the extrusion of a polymersolution through a spinneret.

Polyoxadiazole useful in this invention include any polyoxadiazolepolymer which has suitable properties to allow it to be solution spuninto a fiber from a solvent in which the second polymer can similarly bespun into a fiber can be used to produce composite fibers of thisinvention. Preferably, the polyoxadiazole polymers are1,3,4-polyoxadiazole polymers or copolymers. More preferably, thepolyoxadiazole polymers including copolymers include but are not limitedto polyoxadiazoles comprising the repeat units:

Processes for the production of polyoxadiazole polymers are well knownin the art. Examples of processes for the production of polyoxadiazole(POD) polymers can be found in the Journal of Polymer Science: Part A,3, 45-54 (1965), Journal of Polymer Science: Part A-1, 6, 3357-3370,(1968), Advanced Materials, 9(8), 601-613, (1997) and U.S. patentapplication Ser. No. 11/415,026. It is preferred to have apolyoxadiazole polymer of high inherent viscosity such as those producedby the method disclosed in U.S. patent application Ser. No. 11/415,026.

The second polymer can be any polymer selected from known flexible chainpolymers which include copolymers, but preferred polymers are those thatform isotropic solutions in mineral acids, including chlorosulfonic acidand fluorosulfonic acid, particularly sulfuric acid. A highly preferredpolymer for use in the isotropic solution is polyvinylpyrrolidione(PVP). Examples of suitable polymers include aliphatic polyamides (e.g.,6-nylon, 6,6-nylon, and 6,12-nylon), polyaniline, polyether ketoneketone (PEKK), aromatic polyamides (MPD-I, MPD-I/T), and copolymers ofPVP, such as PVP/VA (Vinyl Acetate).

Polyoxadiazole polymers and flexible chain polymers can be combined inany ratio that allows the solution to be spun into a fiber. Typically,any ratio of polyoxadiazole polymer to flexible chain polymer can bespun into a fiber. One in the art will typically use the rule ofmixtures to determine the ratio of the polymers that will produce afiber with desired properties. Typically, each polymer will be presentby weight in the amount of at least 2 percent in order to produce ameasureable change in properties of the resulting composite fiber.

Composite fibers of this invention can be spun by the process ofcontinuously combining an isotropic polymer solution of a polyoxadiazolepolymer and an isotropic solution of a second polymer to form a combinedpolymer solution; passing the combined polymer solution through at leastone static mixer to form a spin dope; and extruding the spin dopethrough a spinneret to form a composite fiber. Additionally, the processcan further include passing the composite fiber through an air gap;contacting the composite dope fiber with a quench solution to form acoagulated composite fiber; contacting the coagulated composite fiberwith a wash solution; contacting the washed composite fiber with aneutralization solution to form a neutralized and washed compositefiber; drying the neutralized and washed composite fiber; and winding upthe dried composite fiber. The dried composite fiber can be wound onto abobbin on a windup device. Extrusion processes suitable for use inmaking composite fibers within the scope of the present invention aredisclosed in U.S. Pat. Nos. 4,340,559, 4,298,565 and 4,965,033.

The polyoxadiazole composite fibers exhibit improved dyeability overfibers of polyoxadiazole polymers alone. The composite fibers can besolution dyed using both basic or acidic dyes. Basic dyes (or cationicdyes) are used to check the dyeability of the composite fibers. Cationicdyes such as Basacryl Red GL (Basic Red 29 by Color Index) arefrequently used for this purpose because of the depth of the color itgenerates. Dyes are usually soluble in most of organic solvent and inaqueous medium, but dyeability was tested in aqueous medium. Slightacidity (pH of 4-6) is required to achieve level dyeing with basic dyes.

Without being bound to any theory it is believed that improveddyeability of the composite fiber is due to a diffusive channel createdby chain mobility of the flexible chain polymer.

The UV stability of polyoxadiazole composite fibers is typicallyimproved over fibers of polyoxadiazole alone. Polyoxadiazole fibersalone when exposed to a Xenon lamp for 20 hours typically do not exhibitmeasureable tenacity. Composite fibers of polyoxadiazoles having atleast 2 percent by weight of the second polymer when exposed to UVradiation using a Xenon lamp for 20 hours can retain measureabletenacity. Preferably, polyoxadiazole composite fibers contain asufficient amount of the second polymer to retain greater than 20percent of their tenacity after 20 hours of exposure to a Xenon lamp.More preferably, polyoxadiazole composite fibers contain a sufficientamount of the second polymer to retain greater than 35 percent of theirtenacity after 20 hours of exposure to a Xenon lamp. Most preferably,polyoxadiazole composite fibers contain a sufficient amount of thesecond polymer to retain greater than 50 percent of their tenacity after20 hours of exposure to a Xenon lamp.

Each polymer solution and/or the combined stream can contain additivessuch as anti-oxidants, lubricants, ultra-violet screening agents,colorants and the like which are commonly incorporated.

All percentages are by weight unless otherwise indicated.

EXAMPLE 1

A polyoxadiazole copolymer was prepared by mixing 86.885 grams (0.668moles) solid hydrazine sulfate, 88.74 grams (0.534 moles) of solidterephthalic acid, and 22.18 grams (0.133 moles) of solid isophthalicacid were mixed and blended together in a mixer for 30 min. To thisblended mixture of solids was added a first addition of 30% Oleum, 534grams Oleum (2.001 moles of SO3) at 25 degrees Celsius.

The mixture was mechanically stirred at 25 degrees Celsius for 15minutes to dissolve the solids and form a solution. The solution wasthen heated to 120 degrees Celsius with mechanical stirring until aconstant torque (constant viscosity) was observed on the mixer (60minutes).

To this solution was added a second addition of 30% Oleum, 611 gramsoleum (2.290 moles of SO3) at 130 degrees Celsius. The temperature wasmaintained at 130 degrees Celsius for 2 hours until the viscosity of thesolution reached a plateau. The solution was then cooled to roomtemperature.

A small sample was removed from the cooled solution and added to waterat 0 degrees Celsius to precipitate the polymer. The polymer was washedwith water until a neutral pH was reached. The polymer was dried undervacuum and an inherent viscosity of 2.60. The solution was diluted to5.0% solid by adding 581 grams of concentrated sulfuric acid.

To the rest of polymer solution prepared above, 5.06 grams of K-90polyvinylpyrrolidone powder with a weight average molecular weight ofabout 90,000 was added at room temperature and stirred until all addedsolid was dissolved. The solution showed some shear opalescence andsilky appearance. This solution was spun into fiber by air-gap spinninginto coagulation bath of 7% sulfuric acid solution at room temperaturefollowed by washing and neutralized in sodium bicarbonate. The resultingfiber was dried overnight in 120 C oven. Dyeability of the fiber wastested in 0.5% Basacryl Red GL (a basic dye) solution in acidic pH=4-5.The fiber was dyed deep, while the fiber prepared without added PVP wasnot dyed.

EXAMPLE 2

The fiber sample prepared the same way except that low molecular weightPVP (K-30 with a weight average molecular weight of about 60,000)instead of K-90, was also dyed deep with Basacryl Red GL (a basic dye).

1. A composite fiber comprising: at least one polyoxadiazole polymer;and at least one flexible chain polymer, wherein, the flexible chainpolymer is not a polyoxadiazole polymer.
 2. The composite fiber of claim1, wherein: the polyoxadiazole polymer comprises a repeat unit selectedfrom the list consisting of


3. The composite fiber of claim 2, wherein: the polyoxadiazole polymercomprises at least two repeat units selected from the list consisting of


4. The composite fiber of claim 1, wherein: the flexible chain polymeris selected from the list consisting of 6-nylon, 6,6-nylon, 6,12-nylon,polyaniline, polyether ketone ketone (PEKK), aromatic polyamides,polyvinylpyrrolidione (PVP), and copolymers of polyvinypyrrolidione(PVP).
 5. The composite fiber of claim 4, wherein: the flexible chainpolymer is polyvinylpyrrolidione or a copolymer ofpolyvinylpyrrolidione.
 6. The composite fiber of claim 1, wherein: thepolyoxadiazole polymer is a copolymer.
 7. The composite fiber of claim6, wherein: the polyoxadiazole copolymer comprises at least two aromaticring systems selected from the list consisting of:


8. The composite fiber of claim 1, wherein: the composite fiber retainsat least 15 percent of its tenacity after exposure to a Xenon lamp for20 hours.
 9. The composite fiber of claim 1, wherein: the compositefiber is dyeable.
 10. The composite fiber of claim 1, wherein: theflexible chain polymer is present in an amount between about 2 and 98percent by weight.
 11. The composite fiber of claim 10, wherein: theflexible chain polymer is present in an amount between about 5 and 98percent by weight.
 12. The composite fiber of claim 10, wherein: thecomposite fiber retains at least 15 percent of its tenacity afterexposure to a Xenon lamp for 20 hours.
 13. The composite fiber of claim10, wherein: the composite fiber retains at least 35 percent of itstenacity after exposure to a Xenon lamp for 20 hours.
 14. An articlecontaining the composite fiber of claim 1.